Abstract

Our aging society is confronted with a dramatic increase of patients suffering from tauopathies, which include Alzheimer disease and certain frontotemporal dementias. These disorders are characterized by typical neuropathological lesions including hyperphosphorylation and subsequent aggregation of TAU protein and neuronal cell death. Currently, no mechanism-based cures are available. We generated fluorescently labeled TAU transgenic zebrafish, which rapidly recapitulated key pathological features of tauopathies, including phosphorylation and conformational changes of human TAU protein, tangle formation, neuronal and behavioral disturbances, and cell death. Due to their optical transparency and small size, zebrafish larvae are well suited for both in vivo imaging and drug development. TAU-induced neuronal cell death was imaged by time-lapse microscopy in vivo. Furthermore, we used this zebrafish model to identify compounds targeting the TAU kinase glycogen synthase kinase 3β (GSK3β). We identified a newly developed highly active GSK3β inhibitor, AR-534, by rational drug design. AR-534 reduced TAU phosphorylation in TAU transgenic zebrafish. This transgenic zebrafish model may become a valuable tool for further studies of the neuropathology of dementia.

Figure 5

(A–G) Whole-mount immunostainings for znp1, which labels synaptotagmin in the extending axons of primary motoneurons. Expression of TAU causes a dramatically reduced extension of znp1-positive motoneurons already at 28 hpf (A and B). The difference in motoneuron length is quantified (C) by measuring the length of the first 4 znp1-stained motoneuron projections (marked 1, 2, 3, 4 in A and B) before the end of the yolk extension (marked by dotted line). Triangles and diamonds represent values from individual motoneurons; colored horizontal lines represent mean ± SD. ***P < 0.01. In 48-hour-old embryos, the motoneurons have grown further in both TAU fish and controls, but the motoneuron extensions are still reduced (D and E). 5 days later, the motoneurons have grown around the muscle in both TAU fish and controls (F and G). The fine projections of motoneurons (see enlarged insets, arrowheads), are still highly reduced in TAU transgenic fish. Lateral views of the trunk above the end of the yolk extension, anterior to the left. Scale bars: 50 μm. (H–J) The stereotypic escape response, which is normal in DsRed-expressing (H) and nontransgenic larvae at 48 hpf (data not shown), is highly reduced or absent in TAU-expressing larvae (I; see also Supplemental Video 2). The phenotype was quantified in groups of 50 TAU/DsRed versus DsRed transgenic larvae, which were pooled from several clutches and selected for strong and comparable DsRed expression (J). Error bars represent mean ± SD; ***P < 0.01.